Recent results on Atomospheric Neutrino Oscillation from Super-Kamiokande Yoshihisa Obayashi Kamioka Observatory, ICRR, Univ. of Tokyo for the Super-Kamiokande Collaboration
Feb 08, 2016
Recent results on Atomospheric Neutrino
Oscillation from Super-Kamiokande Yoshihisa Obayashi
Kamioka Observatory, ICRR, Univ. of Tokyofor the Super-Kamiokande Collaboration
Super-Kamiokande
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK 2
Imaging Water Cherenkov detector
50kt Pure Water 32kt Inner Detector viewed
by20inch PMTs. Num of tubes:11146(SK-I), 5200(-II), 11129(-III,IV)
t~2m Outer Detector viewed by1885 8inch PMTs
42 m
39.3 m
1000m(2700m.w.e.)
Mt. Ikenoyama (1396m)Kamioka, Japan
SK
Acrylic (front)+ FRP (back)
SK-I SK-II SK-III
SK-IV
1996- 2002- 2006- 2008-
Elec. Upgrade
3
Atmospheric Neutrinoproton
p,K,…
mnm
ene
nm
nm/ne ~ 2 @En<a few
GeV
cosq=-1(upgoing)L~13000km
cosq=1(downgoing)L~15km cosq=
0
Zenith angle distribution~Up/Down symmetric(In the case of NO oscillation)
ne nm
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Event Topology
Energy spectrum of neutrino
FC PC UP-Stopmu UP-Thrumu
4
Up-going Muons
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Particle Identification
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK 5
Identify Electron-like(Showering) particles and Muon-like particles using Cherenkov ring Pattern and Angle likelihood
DATAMC(ALL)MC(nm CCQE)
Muon Decay Electron
Zenith angle & lepton momentum distributions
6
SK-I+II+IIInm–nt oscillation (best fit)null oscillation
Sub-GeV samples are divided to improve sensitivity to low-energy oscillation effects
Live time:SK-I 1489d (FCPC) 1646d (Upmu)SK-II 799d (FCPC) 827d (Upmu)SK-III 518d (FCPC) 636d (Upmu)
m-likee-likemomentum Preliminar
y
Jul. 24, 2010
7
2-flavor oscillation analysis results
Results of both zenith angle analysis and L/E analysis are consistent. SK provides the most stringent limit for sin2(2θ23).
SK-I+II+IIIPreliminary
Zenith Physical Region (1s)Dm23
2=2.11+0.11/-0.19 x10-3
sin22q23>0.96 (90%C.L.)
L/E Physical Region (1s)Dm23
2=2.19+0.14/-0.13 x10-3
sin22q23>0.96 (90%C.L.)
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
8
Full 3-flavor oscillation analysisConsider both matter effect and solar term simultaneously.Matter effect: possible enhancement of ne is expected in several GeV
energy region and in Earth core q13 and mass hierarchy could be studied.
Solar term: possible enhancement of ne in sub-GeV region q23 octant degeneracy could be studied. Interference: CP phase could be studied. (when sin2q13 >~0.05).
MatterSolar term
Interference
Full 3-f osc. analysis: all parameters are considered simultaneously.
PRD81, 092004: either matter effect or solar term is considered with approximations (cannot test the interference part)
Interference
Matter effectSolar term
Difference in # of electron events:
(The nm flux difference is also expected.)
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
99% C.L.90% C.L.68% C.L.best
Excluded byCHOOZ at 90% C.L.
Full 3-flavor oscillation results
9
SK-I+II+III- Normal hierarchy -
Preliminary
10.84 0.40 0
- Inverted hierarchy -
.0015
.0035
300.0015
.0035
.0015
.0035
.0015
.0035
0
0.4
0
0.4
Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
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- Normal hierarchy - Parameter Best point 90% C.L. allowed 68% C.L. allowed
∆m223 (x103) 2.11 eV2 1.88 - 2.75 eV2 1.99 - 2.54 eV2
sin2q23 0.525 0.406 - 0.629 0.441 - 0.597sin2q13 0.006 < 0.066 < 0.036CP- 220º - 140.8 - 297.3º
- Inverted hierarchy - Parameter Best point 90% C.L. allowed 68% C.L. allowed
∆m223 (x103) 2.51 eV2 1.98 - 2.81 eV2 2.09 - 2.64 eV2
sin2q23 0.575 0.426 - 0.644 0.501 - 0.623sin2q13 0.044 < 0.122 0.0122 - 0.0850CP- 220º 121.4 - 319.1º 165.6 - 280.4º
2min =
468.34/416dof
2min =
469.94/416dof
SK-I+II+IIIFull 3-flavor oscillation results
No significant preference on hierarchy.No significant constraint on CP phase at 90%
C.L.
Preliminary
(sin2 q12 , Dm212) are
fixedat (0.304, 7.66x10-5 eV2) Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Full 3-flavor (NH)(1.88< Dm2
23 <2.75) e-30.406 < sin2q23< 0.629
(0.93 < sin22q23 )
Global-best(2.22<Dm2
23<2.60) e-30.401 < sin2q23< 0.615
(0.95 < sin22q23 )
2-flavorFull 3-flavor 99%C.L.
90%C.L.
68%C.L.
2 -2min distributions
Consistent results are obtained.No deviation of sin2q23 from 0.5.Allowed region of Dm2
23 is a bit larger than that of the 2-flavor analysis as the effect of CP phase is also taken into account.
2-flavor (90%)
Full 3-flavor (90%)
Comparison with 2-flavor analysis
90%C.L. allowed region (1dof, 2=2
min+2.71)
99% C.L.90% C.L.68% C.L.best
Jul. 24, 201011 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
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Comparison of Hierarchies
Best fit is in the inverted hierarchy caseNormal hierarchy (NH):2
min= 469.94/416dofInverted hierarchy (IH):2
min= 468.34/416dof ∆2 = 1.6 No significant difference
Multi-GeV samples tend to favor inverted hierarchy.
There are also some contributions from Multi-GeV m-like samples favoring IH to NH.
• NH• IH
Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Search for CPT violation in atm. n Under the CPT theorem, P(n n) and P(n n) should be
same. Test n oscillation or n oscillation separately.
13
SK-I+II+IIIPreliminary
No evidence for CPT violating oscillations is found
Anti-neutrino:
Neutrino: Dm23
2=2.2x10-3eV2
sin22q23=1.0
Dm232=2.0x10-3eV2
sin22q23=1.0
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
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Improvements of the DAQ system
NewElectroni
cs(QBEE)
Readout (Ethernet)
Periodic trigger(60kHz)
Clock
Event build with variabletime windows
SK-I,II,III: partial data above threshold (Num. of hits) were read (1.3msec window x3kHz)SK-IV: All hits above pulse height threshold are read, then apply complex triggers by software.
Collect all hits every 17msec . PMTsignals
Typical event time windows: Super-Low-Energy (SLE) events (<~6.5MeV): -0.5/+1.0msec Normal events(>~6.5MeV): -5/+35msec Supernova Relic n (SRN) candidates(>~10MeV, No OD): -5/+535msec T2K events: -512/+512msec at T2K beam spill timing
high rate (~3kHz) decay electrons
neutrons
Wider dynamic range for charge measurement of each channel (>2000pC)No dead time up to ~6MHz/10sec for Supernova burst neutrinosApply precise event reconstruction to remove more low-e BG events in real-time
Precise analysis in parallel in real-time
x5x100
IEEE Trans. Nucl. Sci. 57 (2010) 428
T2K GPS from J-PARC
Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK15
Muon Decay Electron Tagging
Jul. 24, 2010
SK-III (1.3us gate width) SK-IV (40us gate width)
Detection Efficiency= 72.6%
Detection Efficiency= 88.4%
Expected decay curveIdentified data
Expected decay curveIdentified data
Parent muon
Decay Electront~2us
Wider gate width of SK-IV enables detectionof muon decay electronsat T~1us efficiently
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Zenith angle distributions of SK-IV atm. n
SK-IV
Sub-GeV
Multi-GeV
Sub-GeV
Multi-GeV PC
e-like m-like
StableData taking!
nm–nt oscillationnull oscillation
SK-IV 449 days data
Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK 17
SUMMARY
Jul. 24, 2010
Recent update on Atmospheric neutrino oscillation from SK-I,II,III 2 Flavor nm-nt oscillation result Full 3 Flavor including Solar term & CP, Mass Hierarchy
“Consistent with 2 flavor result, No preference of Hierarchy
CPT violations search “No evidence” Electronics Upgrade (SK-IV)
Improvement on Decay-electron tagging efficiency Stable Atmospheric neutrino data taking
Super-Kamiokande Talk/Posters M. Miura(Nucleon decay) 24-Jul-2010 09:20; BSM Session H. Sekiya(Solar neutrino) Poster M. Smy (Low-energy anti neutrino detection) Poster
BACKUP SLIDES
19
nt appearance searchPRL97,171801 (2006)
Tau MCBKG MCData
t
nt
multi ring
decay-e
t-like selection; efft=43%, S/N=5%
(Downward going)
Likelihood variables
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
(a) Visible Energy(b) Max. decay-e distance from vertex(c) Ring Candidates(d) Sphericity in the lab frame(e) Clustered sphericity in COM frame
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nt appearance search
Best-fit tau excess: 138+/-48(stat.)+15/-
32(syst.) Expected: 78+/-26(syst.)
PRL97,171801 (2006)zenith angle distribution of tau enrich sample
tau enrich sample is consistent with nm-nt oscillation
Data BKG MC Tau MC Generated in fiducial volume - 17135 (100%) 78.4 (100%) Evis > 1.33 GeV 2888 2943 (17.2%) 51.5 (65.7%) Most Energetic ring e-like 1803 1765 (10.3%) 47.1 (60.1%) Likelihood > 0.0 649 647 (3.79%) 33.8 (43.1%) Neural network > 0.5 603 577 (3.36%) 30.6 (39.0%)
(Likelihood)
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
History 1983 Kamiokande started
observationto search for Proton decay
1987 Kamiokande observed SN1987a
1991 Construction of SK started 1996 SK started observation 1998 “Evidence for oscillation of
atmospheric neutrinos” 1999 K2K started 2001 Accident 2002 Partial reconstruction
SK-II startedK2K-II started (-2004)
2006 Full reconstructionSK-III started
2008 Replacement of DAQ electronics
SK-IV Started 2009 T2K started
Kamiokande SK hall excavation(1994)
Filling water (1996)
Accident(2001)
“Evidence…”(1998)
SK-III starts soon(2006)
SK-II starts soon(2002)
21 Jul. 24, 2010Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK
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Atotsu Entrance
Super-Kamiokande
XMASS(Mar. 2008~)
KamLAND(Tohoku Univ.)
IPMU APIMS GC Ge det. Rn det. …(Mar.08~)
40m
CANDLES(Mar. 2008~)
CLIO (Gravitational Wave)Laser extensometer (Geophysics)
Gadolinium project R&D(10mx15mx8~9mh,March 2010~) NEWAGE
Superconductive gravimeter
Kamioka Underground Site
Jul. 24, 2010 Yoshihisa OBAYASHI, Atmospheric Neutrino from SuperK